EFFECTS OF VARYING DISCHARGE AND VARYING DIAMETER ON DISCHARGE COEFFICIENT OF ORIFICE

Abstract

Hydroelectric power plants are the main pillars for any country in order to generate electricity. India is committed to promote hydropower and aiming to establish hydropower generation capacity of 70,000 MW by 2030. By increasing the installed capacity of power plants, it might become beneficial for the flexibility of hydroelectric power plants and by increasing the height of dam it can boost the production of electricity in time of high demand around the country. These kinds of modifications in already existed power plants may cause mass oscillations in the waterways system. Hence, to avoid the damage due to mass oscillations throttling the surge tank is beneficial to control the increasing discharge in the system. Orifices are very important part of the surge tank in hydro power plants in order to make whole facility safer and make it more suitable. Several factors affect the performance of orifice such as discharge through orifice, level of head, geometry of orifice as well as rounded or sharp edges of orifice. In order to make best use of orifice in the surge shaft to avoid future damages from water hammer and mass oscillations phenomena, we must design orifices carefully. In the present study, an orifice of 13 cm diameter is placed at the bottom of the surge shaft. Study is carried out to observe the change in discharge coefficient with different flow through orifice by evaluating the head losses across the orifice. In order to do so, twelve piezo points connected with glass manometer tubes to observe the mean pressure at those points. Results show that discharge coefficient shows increasing trend with increasing flow through orifice.